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Mesopore quality determines the lifetime of hierarchically structured zeolite catalysts

2014; Nature Portfolio; Volume: 5; Issue: 1 Linguagem: Inglês

10.1038/ncomms4922

2041-1723

Maria Milina, Sharon Mitchell, P. Crivelli, D. Cooke, Javier Pérez‐Ramírez,

Chemical Synthesis and Characterization

Deactivation due to coking limits the lifetime of zeolite catalysts in the production of chemicals and fuels. Superior performance can be achieved through hierarchically structuring the zeolite porosity, yet no relation has been established between the mesopore architecture and the catalyst lifetime. Here we introduce a top-down demetallation strategy to locate mesopores in different regions of MFI-type crystals with identical bulk porous and acidic properties. In contrast, well-established bottom-up strategies as carbon templating and seed silanization fail to yield materials with matching characteristics. Advanced characterization tools capable of accurately discriminating the mesopore size, distribution and connectivity are applied to corroborate the concept of mesopore quality. Positron annihilation lifetime spectroscopy proves powerful to quantify the global connectivity of the intracrystalline pore network, which, as demonstrated in the conversions of methanol or of propanal to hydrocarbons, is closely linked to the lifetime of zeolite catalysts. The findings emphasize the need to aptly tailor hierarchical materials for maximal catalytic advantage. Zeolite catalysts are industrially important, but may be deactivated by coking. Here, the authors demonstrate the effectiveness of top-down demetallation approaches in controlling mesopore formation, using a range of techniques to probe the resulting structures and assess the effects on catalyst lifetime.